Persistent configuration should only be updated by currentUser

On auto devices, it is possible that multiple users are visible simultaneously using visible background users. In such cases, it is desired that only the current user (and not the visible background user) can change the locale and other persistent settings of the device.

Bug: 322229751
Test: atest LocalePickerTest
Test: atest --user-type secondary_user_on_secondary_display LocalePickerTest
Test: atest --user-type secondary_user LocalePickerTest
Change-Id: I11d86e2f7cb9ba0f16b34cdf629557abea3a29ce